1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing a liquid container in which any of various liquids is contained, such as an ink tank in which ink is contained.
2. Description of the Related Art
In a liquid ejection apparatus using a liquid ejection head capable of ejecting a liquid such as ink, a liquid container in which a liquid is contained is connected to an upstream side of a supply system for supplying the liquid to the liquid ejection head. For example, in an ink jet printing apparatus (liquid ejection apparatus) using an ink jet print head (liquid ejection head) capable of ejecting ink, an ink tank (liquid container) in which ink is accommodated is removably connected to an upstream side of an ink supply system.
Some ink tanks in such ink jet printing apparatuses include a first chamber R1 in which an ink absorber as a negative pressure generating member 1 (1A and 1B) is accommodated, and a second chamber R2 in which ink is directly accommodated, as shown in FIG. 5 and FIG. 6. The first and second chambers R1 and R2 are in communication with each other via a communication portion 2A formed in a partition wall 2. FIG. 5 is a cross-sectional view of the ink tank in which no ink is contained. FIG. 6 is a cross-sectional view of the ink tank in which ink is contained.
As a method for filling ink into such an ink tank, a filling method described in Japanese Patent Laid-Open No. 11-48490 is known. In the filing method, first, an ink supply port 3 and an atmospheric communication port 4 are closed. Then, a pump 5 is used to discharge air from the ink tank in a direction of arrow A through an ink filling hole 6 and a valve 7, thus reducing the pressure in the first and second chambers R1 and R2. Thereafter, the valve 7 is closed, and a pump 8 is used to feed ink 20 from an ink reservoir 9 in a direction of arrow B to fill the ink 20 into the second chamber R2 through a valve 10 and the ink filling hole 6. At this time, the ink 20 permeates only a part of a surface of the negative pressure generating member 1 in the first chamber R1 through a communication portion 2A. Then, the valve 10 is closed, and the pump 8 is used to feed the ink 20 from the ink reservoir 9 in a direction of arrow C to fill the ink 20 into the first chamber R1 through a valve 12 and the ink supply port 3. The ink 20 in the first chamber R1 is absorbed and held by the capillary force of the negative pressure generating member 1. Thereafter, the ink supply port 3 is closed, and the atmospheric communication port 4 is opened to completely cancel the reduced pressure state in the first and second chambers R1 and R2 (the first and second chambers R1 and R2 are open to the atmosphere). A ball 11 then close the ink filling hole 6.
The ink supply port 3 of the ink tank with the ink thus filled therein is connected to an ink jet print head (not shown in the drawings). The ink 20 absorbed and held in the first chamber R1 by the negative pressure generating member 1 is supplied to the print head, with a negative pressure applied to the ink 20. As the ink 20 is supplied, the ink in the second chamber R2 is fed into the first chamber R1 through the communication portion 2A. A corresponding amount of air is fed from the atmospheric communication port 4 into the second chamber R2 through an atmospheric introducing channel 13 and the communication portion 2A.
However, when the ink is filled into the ink tank, a portion P permeated by the ink 20 mixed with air may be generated near the partition wall 2 in the negative pressure generating member 1. Such a phenomenon occurs when the first and second chambers R1 and R2 are opened to the atmosphere, that is, when the atmospheric communication port 4 is opened to completely cancel the reduced pressure state in the ink tank, causing the ink 20 in the first chamber R1 to be pressed downward in FIG. 6 by the atmospheric pressure. That is, the ink in the first chamber R1 mainly flows from a position near the partition wall 2 through the communication portion 2A into the second chamber R2. To make up for the ink 20 having flown into the second chamber R2, the ink gathers at the position near the partition wall 2 from the entire negative pressure generating member 1. At this time, if a portion of the negative pressure generating member 1 which is located near the partition wall 2 fails to have the appropriate density, the portion offers reduced flow resistance, thus increasing the speed at which the ink 20 flows into the second chamber R2 through the portion and the communication portion 2A. The air having entered the first chamber R1 through the atmospheric communication port 4 flows into the portion near the partition wall 2 so as to be entrained in the ink flowing in at high speed. As a result, the ink 20 and the air are mixed together in the portion P of the negative pressure generating member 1 which is located near the partition wall 2.
If immediately after ink filling or during a distribution process after shipment, an impact is made on the ink tank with the ink 20 and the air mixed together in the portion P of the negative pressure generating member 1 as described above, a gas-liquid exchange is likely to occur through the communication portion 2A so as to fill the portion P with the ink. That is, the air present in the portion P is likely to be exchanged with the ink 20 in the second chamber R2 through the communication portion 2A. If such a gas-liquid exchange occurs, the volume of air bubbles 30 present in the second chamber R2 increases.
The air bubbles 30 present in the second chamber R2 expand with a rise in temperature or a decrease in atmospheric pressure. Thus, an amount of the ink 20 in the second chamber R2 corresponding to the expanded volume flows into the first chamber R1 and is absorbed by the negative pressure generating member 1. However, if the amount of the ink 20 flowing into the first chamber R1 exceeds the amount of the ink absorbed by the negative pressure generating member 1, the ink may leak from the ink supply port 3 when a seal (not shown in the drawings) is torn off to allow the use of the ink tank to be started. Thus, when the ink tank is shipped, the volume of the air bubbles 30 present in the second chamber R2 needs to be appropriately managed. However, if the amount of the air bubbles 30 increases as a result of an additional amount of air from the portion P with the ink and the air mixed therein, the amount of the air bubbles 30 may exceed the range of values within which the amount can be appropriately managed.
A possible measure for preventing generation of the portion P with the ink and the air mixed therein is to increase the duration of the operation of opening the chambers to the atmosphere when the ink is filled into the chambers. That is, the reduced pressure state in the ink tank may be gradually canceled to reduce the force of the atmospheric pressure pressing the ink and thus the speed at which the ink 20 flows from the first chamber R1 into the second chamber R2 is downed so that the ink 20 can be fed from the entire negative pressure generating member 1 into the second chamber R2. However, to achieve this, the duration of the operation of opening the chambers to the atmosphere needs to be set to at least several tens of seconds. This reduces the efficiency of the ink filling operation and thus the productivity of the ink tank.